The goal of the next five years is to understand the molecular basis for the cyclic activity of the fat body of the mosquito, Aedes aegypti. Previously they have succeeded in dissecting the biosynthetic pathway of vitellogenin (Vg) and discovered a novel vitellogenic protein 53KP. The goal for the next five years is to study the regulation of expression of several key genes in the fat body. To that end, cloning of full length cDNAs corresponding to these genes will be obtained. Using these cDNA probes, together with nuclear run on transcription and dot blot hybridization assays, the kinetics and regulation of gene expression will be investigated. A combination of in vivo and in vitro hormone treatments of fat body will be utilized to determine the role of 2O-hydroxyecdysone in the initiation and maintenance of expression of the genes and in the stabilization of their mRNAs, and to identify factors responsible for the termination of gene expression. Biochemical and biosynthetic characterization of yolk protein precursors Vg and 53KP will continue.